Background: To assess the influence of β2-receptor
suppression on top of selective β1-receptor blockade on the occurrence of vascular events and on all-cause mortality in patients with acute coronary syndrome (ACS) or heart failure (HF ). Methods: Systematic review of studies published since 1980. Randomised controlled trials directly comparing β1 blockers with β1+2 blockers, or comparing the two
β blockers with placebo, were included. Studies had a minimum treatment period of three months and total mortality or vascular events as their primary or secondary outcome. Results: Of the included studies, five directly compared β blockers (3733 patients) and 28 compared β blockers with placebo (30,889 patients). These latter studies were heterogeneous in study population, dose and type of β blockers. In ACS, the only study directly comparing different β blockers was underpowered to detect a difference
on mortality, while in HF β1+2 blockers significantly
decreased mortality compared with b1 blockers (RR 0.86, 95% confidence interval 0.78 to 0.94). In ACS, β1 blockers in placebo-controlled trials non-significantly reduced total mortality (RR 0.82, 0.67 to 1.01) or vascular events (RR 0.68, 0.42 to 1.11), while β1+2 blockers were associated with a significant decrease in total mortality (RR 0.73, 0.64 to 0.82), and vascular events (RR 0.71, 0.59 to 0.84). In HF, β1 and β1+2 blockers reduced total mortality, while only β1+2 blockers decreased vascular events (RR 0.80, 0.64 to 1.00). Conclusions: Additional β2-receptor blockade may be more effective than β1-receptor blockade alone in preventing total mortality and vascular events in patients with ACS or, to a lesser extent, HF . However, only a few studies directly compared β blockers, and indirect comparisons were subject to heterogeneity, which weakens firm conclusions.